In this article, we will discuss the basic layout and diagram of the thermal power plant. A power plant has various components, like alternators, transformers, turbines, etc., to produce electrical energy. Based on the fuel used in a power plant to produce electrical energy, there are several types of power plants, such as thermal power plants, nuclear power plants, hydroelectric power plants, gas turbine power plants, and more. This article explains the basic structure of a thermal power plant and its working.
Table of contents
Basic Layout of Thermal Power Plant
The basic layout and diagram of a thermal power plant are shown in the following figure.
Components of Thermal Power Plant
The diagram of a thermal power plant consists of the following major components:
- Coal storage and pulverizer
- Water Boiler
- Steam Turbine
- Alternator
- Condenser
- Feed water pump
- Chimney
Let us discuss the functioning of these components in a thermal power plant.
(1). Coal Storage and Pulverizer:
In a thermal power plant, there is a dedicated space where the coal is brought from coal mines. The coal may contain iron particles that may damage the equipment, and therefore, the coal is first cleaned in a magnetic cleaner to remove the iron particles.
The pulverizer is a system used to crush the raw coal into small particles to convert it into coal powder. This is an essential process that ensures the complete combustion of the coal. The ash produced after coal combustion is removed from the boiler. The ash is known as fly ash, and cement industries use it to produce cement.
(2). Water Boiler:
A boiler is a device used to produce steam from water. In the boiler, there is a combustion chamber where the pulverized coal is burnt.
The coal and preheated air are burned in the combustion zone. When coal is ignited in the boiler, a large fireball forms at the center, releasing a huge amount of heat energy and high-temperature flue gases. The water flows through the steel tubes that run along the boiler walls. The flue gases heat the water and pass through the superheater, economizer, and air preheater, and, finally, exhaust from the chimney in the atmosphere.
Let us have a brief overview of the superheater, economizer, and air preheater.
Superheater:
The superheater tubes are a group of tubes located in the hottest part of the boiler. The boiler tubes produce the saturated steam, and to increase its enthalpy, the steam is superheated in a superheater at around 540 °C. The superheated high-pressure steam is then fed to the steam turbine.
Air pre-heater:
The air is used for combustion of the coal in the boiler. The primary air fan takes the atmospheric air, and then the air is heated up in the air pre-heater. The coal with preheated air is injected into the boiler. The preheated air improves the coal combustion in the boiler.
Economizer:
An economizer recovers waste heat from the exhausted flue gases and preheats the feed water to increase the boiler’s efficiency. The preheating of water reduces the amount of coal and saves energy.
The heat produced is then transferred to boil the water and produce steam. Overall, the boiler is a piece of equipment that converts water into steam.
(3). Steam Turbine:
A steam turbine is a prime mover that converts the heat and pressure energy of steam into kinetic energy. The superheated and high-pressure steam is passed over the blades of the steam turbine, which causes the turbine to rotate. The steam turbine is further connected to the electric generator and drives the generator to produce electricity.
The steam condenses in a condenser when it passes through the steam turbine, and the pressure and temperature of the steam decrease, causing an increase in volume. The expanded low-pressure steam is exhausted in the condenser.
(4). Condenser:
A condenser condenses the exhaust steam from the turbine by cold water circulation. The steam loses its pressure and temperature, and it is again converted into water. The condenser improves the overall efficiency of the power plant.
(4). Alternator:
An alternator is an electric generator that converts the rotational mechanical energy of the steam turbine into alternating current electricity.
In practice, the alternator produces electricity at 11 kV, which is increased to higher voltages for transmission.
(6). Feed Water Pump:
The feed water pump feeds the condensed water from the condenser to the boiler to produce steam again.
(7). Chimney:
A chimney is the exhaust point of the gases produced due to coal combustion. It is typically made up of bricks and concrete.
The size of the chimney depends on the volume of gases to be exhausted. Chimneys also have a mechanism to filter the exhaust gases before releasing them into the environment so they cause minimal pollution.
It is also important to note that a practical thermal power plant has several other modern components and auxiliary equipment that help maximize the overall plant efficiency.
Working of Thermal Power Plant
After getting a basic understanding of the different components of a thermal power plant, it is straightforward to understand its working or operation.
The complement working of a typical thermal power plant is explained here.
In a thermal power plant, the pulverized coal is burnt in a combustion chamber to produce heat. The boiler then uses this heat to convert water into steam with high temperature and pressure.
The high-pressure superheated steam is passed over the blades of the steam turbine coupled to an electric generator.
The generator coupled to a steam turbine rotates and produces electricity. The generator voltage is stepped up to transmit electrical energy to load points for utilization.
This is the basic process in a thermal power plant to generate electricity.
Advantages of Thermal Power Plant
Thermal power plant has several advantages over other types of power plants. Some key benefits of thermal power plants are given below:
- Thermal power plants utilize coal as fuel to produce heat. Hence, the fuel cost is low as compared to nuclear power plants.
- They can generate massive amounts of electric power to supply significant loads.
- Their operating cost is lower than that of the diesel generating station.
- Thermal power plants utilize less water than hydroelectric power plants.
Disadvantages of Thermal Power Plant
Apart from benefits, thermal power plants also have some downsides. Some key disadvantages of thermal power plants are given below:
- The maintenance cost of thermal power plants is high.
- The exhaust gases pollute the environment.
- Coal and ash handling is complicated.
- The operational cost of thermal power plants is higher than that of hydroelectric power plants.
Conclusion
In conclusion, a thermal power plant is an arrangement of electrical and mechanical equipment that converts the heat energy of coal combustion into electrical energy. For this, it utilizes a steam turbine that drives an electric generator. In this article, we have discussed the basic layout and diagram of a typical thermal power plant.